Triazenides as Suitable Ligands in the Synthesis of Palladium Compounds in Three Different Oxidation States: I, II, and III

Abstract

New orthometalated dinuclear triazenide palladium(II) compounds of the general formula Pd2[(C6H4)PPh2]2[R–N–N–N–R]2 (R = C6H5, 3a; o-BrC6H4, o-3b; o-MeOC6H4, o-3c; o-MeC6H4, o-3d ; p-BrC6H4, p-3b; p-MeOC6H4, p-3c; p-MeC6H4, p-3d) have been synthesized and structurally characterized. The characteristics of these compounds were compared with the isoelectronic formamidinate derivatives. These triazenide compounds have been suitable starting products in the synthesis of new not so common dinuclear palladium(I) compounds and new unusual palladium(III) ones. In the presence of an excess of the triazenide ligand, compounds o-3b and o-3c underwent a reduction process giving dinuclear palladium(I) compounds, Pd2[R–N–N–N–R]2 (R = o-BrC6H4, o-4b; R = o-MeOC6H4, o-4c). DFT calculations verified the importance of the mostly noncovalent Pd···Br or Pd···OMe axial interactions on the stability of these compounds. Under cyclic voltammetric conditions, compounds 3 with the only exception of compound o-3b, were found to und...